Thermal properties of sonicated graphene in coconut oil as a phase change material for energy storage in building applications1

Abstract

This study aims to investigate the thermal properties of a phase change material (PCM) based on coconut oil for building energy storage applications. Coconut oil is classified as an organic PCM composed of fatty acids made from renewable feedstock. However, low thermal conductivity is one of the major drawbacks of organic PCMs that must be improved. Graphene could be an effective material to enhance the thermal performance of organic PCMs. In this study, coconut oil with a latent heat capacity of 114.6 J/g and a melting point of 17.38°C was used. PCMs were prepared by sonicating graphene into coconut oil, as a supporting material. The mass fractions of the prepared PCMs were 0, 0.1, 0.2, 0.3, 0.4 and 0.5. Thermal conductivity tests were performed using a KD2 thermal property analyser under different ambient temperatures of 5, 10, 15, 20 and 25°C simulated with a circulating thermostatic bath. The latent heat, melting point and freezing point were determined through differential scanning calorimetry, the thermal stability was determined using thermogravimetric analysis (TGA) and the morphology and chemical structure were examined using transmission electron microscopy and Fourier-transform infrared spectroscopy, respectively. The results of this study showed that graphene addition to coconut oil improved the thermal performance, with the highest improvement seen in a 0.3 wt% sample at 20°C. The latent heat decreased by 11% owing to molecular movements within the PCM. However, TGA revealed that the composite PCMs showed good thermal stability in ambient building temperature ranges.

Development of Coconut Oil/Capric Acid Eutectic Phase Change Material with Graphene as Latent Thermal Energy Storage

“…Compared to CO-CA eutectic PCMs, the increment in thermal conductivity of CO-CA-G varied from 3-21.7% with respect to the graphene content. The findings in this study are consistent with the findings by Safira et al [8], which found that the thermal conductivity of coconut oil with graphene increased with the increase in graphene concentrations. The high thermal conductivity of graphene and Brownian motion contribute to the increase in the thermal conductivity of the eutectic mixture [9].…”

“…In addition, they usually could be recovered from abundant underused feedstock and are available at low cost [5]. Bio-resourced plant oil such as coconut oil [6], palm kernel oil, Allanblackia, shea butter [7], vegetable fat [5], and beef tallow [8] have also been used as PCMs. Kahwaji and White [9] reported that coconut oil is thermally and chemically stable with acceptable latent heat and melting temperature.…”

“…Besides commonly used fatty acids, coconut oil, margarine, and beef tallow were also used to prepare a eutectic mixture. journal.ump.edu.my/ijame ◄ Thiab et al [8] in his study on thermal properties of coconut oil/beef tallow (BT), found that the latent heat ranged between 72.32-101.05 kJ/kg, which offers a high potential to be used in wall-building applications to control the indoor climate. All these studies indicated that the melting point of the eutectic mixture of fatty acids could be tailored to suit the required application.…”

A comprehensive review on the techniques for coconut oil extraction and its application

“…In year 2020, it was found that when combined with sonicated graphene, coconut oil can serve as a phase change material for energy storage purposes. It was found that the best results for this application may be obtained at low concentrations of graphene at 0.3 wt% graphene [ 76 ]. In recent year, Lugoda found that combining coconut oil and carbon black, a strain sensor can be developed.…”

Thermal Properties and Characterization of n-Decyl-Lauryl Alcohol/Expanded Graphite/Silicon Carbide Composite Phase Change Materials for Refrigerator Cold Energy Storage

“…Safira et al prepared a composite PCM that used coconut oil as PCM and sonicating graphene as thermal conductivity enhancer. Through the test fount that, when the addition amount of sonicating graphene was 0.3 wt.%, its thermal conductivity was increased by 69% compared with pure PCM [20]. Lin et al prepared the palmitic acid (PA)/nanosilica composite PCM with the optimum mass ratio of 70:30, the latent heat of melting (Hm) and the melting temperature (Tm) were 128.42 J/g and 60 ℃, respectively.…”